Noncompact counterexample to the Šura-Bura lemma
ID: noncompact-counterexample-to-the-sura-bura-lemma
Set , , , and let be the polygonal arc joining , , , and . In the planar subspace , each arc is clopen. The component of is therefore just . Any clopen neighborhood of contains the left endpoints of all sufficiently high arcs, hence those entire connected arcs, and by closedness also the limit of their right endpoints. Thus its quasi-component is . Higher arcs escape to infinity while their endpoints approach the two distinguished points.
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